xref: /petsc/src/ts/tutorials/ex46.c (revision 98921bda46e76d7aaed9e0138c5ff9d0ce93f355)

static char help[] = "Time dependent Navier-Stokes problem in 2d and 3d with finite elements.\n\
We solve the Navier-Stokes in a rectangular\n\
domain, using a parallel unstructured mesh (DMPLEX) to discretize it.\n\
This example supports discretized auxiliary fields (Re) as well as\n\
multilevel nonlinear solvers.\n\
Contributed by: Julian Andrej <juan@tf.uni-kiel.de>\n\n\n";

#include <petscdmplex.h>
#include <petscsnes.h>
#include <petscts.h>
#include <petscds.h>

/*
  Navier-Stokes equation:

  du/dt + u . grad u - \Delta u - grad p = f
  div u  = 0
*/

typedef struct {
  PetscInt mms;
} AppCtx;

#define REYN 400.0

/* MMS1

  u = t + x^2 + y^2;
  v = t + 2*x^2 - 2*x*y;
  p = x + y - 1;

  f_x = -2*t*(x + y) + 2*x*y^2 - 4*x^2*y - 2*x^3 + 4.0/Re - 1.0
  f_y = -2*t*x       + 2*y^3 - 4*x*y^2 - 2*x^2*y + 4.0/Re - 1.0

  so that

    u_t + u \cdot \nabla u - 1/Re \Delta u + \nabla p + f = <1, 1> + <t (2x + 2y) + 2x^3 + 4x^2y - 2xy^2, t 2x + 2x^2y + 4xy^2 - 2y^3> - 1/Re <4, 4> + <1, 1>
                                                    + <-t (2x + 2y) + 2xy^2 - 4x^2y - 2x^3 + 4/Re - 1, -2xt + 2y^3 - 4xy^2 - 2x^2y + 4/Re - 1> = 0
    \nabla \cdot u                                  = 2x - 2x = 0

  where

    <u, v> . <<u_x, v_x>, <u_y, v_y>> = <u u_x + v u_y, u v_x + v v_y>
*/
PetscErrorCode mms1_u_2d(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nf, PetscScalar *u, void *ctx)
{
  u[0] = time + x[0]*x[0] + x[1]*x[1];
  u[1] = time + 2.0*x[0]*x[0] - 2.0*x[0]*x[1];
  return 0;
}

PetscErrorCode mms1_p_2d(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nf, PetscScalar *p, void *ctx)
{
  *p = x[0] + x[1] - 1.0;
  return 0;
}

/* MMS 2*/

static PetscErrorCode mms2_u_2d(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nf, PetscScalar *u, void *ctx)
{
  u[0] = PetscSinReal(time + x[0])*PetscSinReal(time + x[1]);
  u[1] = PetscCosReal(time + x[0])*PetscCosReal(time + x[1]);
  return 0;
}

static PetscErrorCode mms2_p_2d(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nf, PetscScalar *p, void *ctx)
{
  *p = PetscSinReal(time + x[0] - x[1]);
  return 0;
}

static void f0_mms1_u(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                      const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                      const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                      PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f0[])
{
  const PetscReal Re    = REYN;
  const PetscInt  Ncomp = dim;
  PetscInt        c, d;

  for (c = 0; c < Ncomp; ++c) {
    for (d = 0; d < dim; ++d) {
      f0[c] += u[d] * u_x[c*dim+d];
    }
  }
  f0[0] += u_t[0];
  f0[1] += u_t[1];

  f0[0] += -2.0*t*(x[0] + x[1]) + 2.0*x[0]*x[1]*x[1] - 4.0*x[0]*x[0]*x[1] - 2.0*x[0]*x[0]*x[0] + 4.0/Re - 1.0;
  f0[1] += -2.0*t*x[0]          + 2.0*x[1]*x[1]*x[1] - 4.0*x[0]*x[1]*x[1] - 2.0*x[0]*x[0]*x[1] + 4.0/Re - 1.0;
}

static void f0_mms2_u(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                      const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                      const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                      PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f0[])
{
  const PetscReal Re    = REYN;
  const PetscInt  Ncomp = dim;
  PetscInt        c, d;

  for (c = 0; c < Ncomp; ++c) {
    for (d = 0; d < dim; ++d) {
      f0[c] += u[d] * u_x[c*dim+d];
    }
  }
  f0[0] += u_t[0];
  f0[1] += u_t[1];

  f0[0] -= ( Re*((1.0L/2.0L)*PetscSinReal(2*t + 2*x[0]) + PetscSinReal(2*t + x[0] + x[1]) + PetscCosReal(t + x[0] - x[1])) + 2.0*PetscSinReal(t + x[0])*PetscSinReal(t + x[1]))/Re;
  f0[1] -= (-Re*((1.0L/2.0L)*PetscSinReal(2*t + 2*x[1]) + PetscSinReal(2*t + x[0] + x[1]) + PetscCosReal(t + x[0] - x[1])) + 2.0*PetscCosReal(t + x[0])*PetscCosReal(t + x[1]))/Re;
}

static void f1_u(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                 const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                 const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                 PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f1[])
{
  const PetscReal Re    = REYN;
  const PetscInt  Ncomp = dim;
  PetscInt        comp, d;

  for (comp = 0; comp < Ncomp; ++comp) {
    for (d = 0; d < dim; ++d) {
      f1[comp*dim+d] = 1.0/Re * u_x[comp*dim+d];
    }
    f1[comp*dim+comp] -= u[Ncomp];
  }
}

static void f0_p(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                 const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                 const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                 PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f0[])
{
  PetscInt d;
  for (d = 0, f0[0] = 0.0; d < dim; ++d) f0[0] += u_x[d*dim+d];
}

static void f1_p(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                 const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                 const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                 PetscReal t, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar f1[])
{
  PetscInt d;
  for (d = 0; d < dim; ++d) f1[d] = 0.0;
}

/*
  (psi_i, u_j grad_j u_i) ==> (\psi_i, \phi_j grad_j u_i)
*/
static void g0_uu(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                  const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                  const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                  PetscReal t, PetscReal u_tShift, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar g0[])
{
  PetscInt NcI = dim, NcJ = dim;
  PetscInt fc, gc;
  PetscInt d;

  for (d = 0; d < dim; ++d) {
    g0[d*dim+d] = u_tShift;
  }

  for (fc = 0; fc < NcI; ++fc) {
    for (gc = 0; gc < NcJ; ++gc) {
      g0[fc*NcJ+gc] += u_x[fc*NcJ+gc];
    }
  }
}

/*
  (psi_i, u_j grad_j u_i) ==> (\psi_i, \u_j grad_j \phi_i)
*/
static void g1_uu(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                  const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                  const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                  PetscReal t, PetscReal u_tShift, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar g1[])
{
  PetscInt NcI = dim;
  PetscInt NcJ = dim;
  PetscInt fc, gc, dg;
  for (fc = 0; fc < NcI; ++fc) {
    for (gc = 0; gc < NcJ; ++gc) {
      for (dg = 0; dg < dim; ++dg) {
        /* kronecker delta */
        if (fc == gc) {
          g1[(fc*NcJ+gc)*dim+dg] += u[dg];
        }
      }
    }
  }
}

/* < q, \nabla\cdot u >
   NcompI = 1, NcompJ = dim */
static void g1_pu(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                  const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                  const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                  PetscReal t, PetscReal u_tShift, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar g1[])
{
  PetscInt d;
  for (d = 0; d < dim; ++d) g1[d*dim+d] = 1.0; /* \frac{\partial\phi^{u_d}}{\partial x_d} */
}

/* -< \nabla\cdot v, p >
    NcompI = dim, NcompJ = 1 */
static void g2_up(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                  const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                  const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                  PetscReal t, PetscReal u_tShift, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar g2[])
{
  PetscInt d;
  for (d = 0; d < dim; ++d) g2[d*dim+d] = -1.0; /* \frac{\partial\psi^{u_d}}{\partial x_d} */
}

/* < \nabla v, \nabla u + {\nabla u}^T >
   This just gives \nabla u, give the perdiagonal for the transpose */
static void g3_uu(PetscInt dim, PetscInt Nf, PetscInt NfAux,
                  const PetscInt uOff[], const PetscInt uOff_x[], const PetscScalar u[], const PetscScalar u_t[], const PetscScalar u_x[],
                  const PetscInt aOff[], const PetscInt aOff_x[], const PetscScalar a[], const PetscScalar a_t[], const PetscScalar a_x[],
                  PetscReal t, PetscReal u_tShift, const PetscReal x[], PetscInt numConstants, const PetscScalar constants[], PetscScalar g3[])
{
  const PetscReal Re    = REYN;
  const PetscInt  Ncomp = dim;
  PetscInt        compI, d;

  for (compI = 0; compI < Ncomp; ++compI) {
    for (d = 0; d < dim; ++d) {
      g3[((compI*Ncomp+compI)*dim+d)*dim+d] = 1.0/Re;
    }
  }
}

static PetscErrorCode ProcessOptions(MPI_Comm comm, AppCtx *options)
{
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  options->mms = 1;

  ierr = PetscOptionsBegin(comm, "", "Navier-Stokes Equation Options", "DMPLEX");CHKERRQ(ierr);
  ierr = PetscOptionsInt("-mms", "The manufactured solution to use", "ex46.c", options->mms, &options->mms, NULL);CHKERRQ(ierr);
  ierr = PetscOptionsEnd();CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode CreateMesh(MPI_Comm comm, DM *dm, AppCtx *ctx)
{
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  ierr = DMCreate(comm, dm);CHKERRQ(ierr);
  ierr = DMSetType(*dm, DMPLEX);CHKERRQ(ierr);
  ierr = DMSetFromOptions(*dm);CHKERRQ(ierr);
  ierr = DMViewFromOptions(*dm, NULL, "-dm_view");CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode SetupProblem(DM dm, AppCtx *ctx)
{
  PetscDS        ds;
  DMLabel        label;
  const PetscInt id = 1;
  PetscInt       dim;
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  ierr = DMGetDimension(dm, &dim);CHKERRQ(ierr);
  ierr = DMGetDS(dm, &ds);CHKERRQ(ierr);
  ierr = DMGetLabel(dm, "marker", &label);CHKERRQ(ierr);
  switch (dim) {
  case 2:
    switch (ctx->mms) {
    case 1:
      ierr = PetscDSSetResidual(ds, 0, f0_mms1_u, f1_u);CHKERRQ(ierr);
      ierr = PetscDSSetResidual(ds, 1, f0_p, f1_p);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 0, 0, g0_uu, g1_uu, NULL,  g3_uu);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 0, 1, NULL, NULL, g2_up, NULL);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 1, 0, NULL, g1_pu, NULL,  NULL);CHKERRQ(ierr);
      ierr = PetscDSSetExactSolution(ds, 0, mms1_u_2d, ctx);CHKERRQ(ierr);
      ierr = PetscDSSetExactSolution(ds, 1, mms1_p_2d, ctx);CHKERRQ(ierr);
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "wall", label, 1, &id, 0, 0, NULL, (void (*)(void)) mms1_u_2d, NULL, ctx, NULL);CHKERRQ(ierr);
      break;
    case 2:
      ierr = PetscDSSetResidual(ds, 0, f0_mms2_u, f1_u);CHKERRQ(ierr);
      ierr = PetscDSSetResidual(ds, 1, f0_p, f1_p);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 0, 0, g0_uu, g1_uu, NULL,  g3_uu);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 0, 1, NULL, NULL, g2_up, NULL);CHKERRQ(ierr);
      ierr = PetscDSSetJacobian(ds, 1, 0, NULL, g1_pu, NULL,  NULL);CHKERRQ(ierr);
      ierr = PetscDSSetExactSolution(ds, 0, mms2_u_2d, ctx);CHKERRQ(ierr);
      ierr = PetscDSSetExactSolution(ds, 1, mms2_p_2d, ctx);CHKERRQ(ierr);
      ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "wall", label, 1, &id, 0, 0, NULL, (void (*)(void)) mms2_u_2d, NULL, ctx, NULL);CHKERRQ(ierr);
      break;
    default: SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_ARG_OUTOFRANGE, "Invalid MMS %D", ctx->mms);
    }
    break;
  default: SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_ARG_OUTOFRANGE, "Invalid dimension %D", dim);
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode SetupDiscretization(DM dm, AppCtx *ctx)
{
  MPI_Comm        comm;
  DM              cdm = dm;
  PetscFE         fe[2];
  PetscInt        dim;
  PetscBool       simplex;
  PetscErrorCode  ierr;

  PetscFunctionBeginUser;
  ierr = PetscObjectGetComm((PetscObject) dm, &comm);CHKERRQ(ierr);
  ierr = DMGetDimension(dm, &dim);CHKERRQ(ierr);
  ierr = DMPlexIsSimplex(dm, &simplex);CHKERRQ(ierr);
  ierr = PetscFECreateDefault(comm, dim, dim, simplex, "vel_", PETSC_DEFAULT, &fe[0]);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject) fe[0], "velocity");CHKERRQ(ierr);
  ierr = PetscFECreateDefault(comm, dim, 1, simplex, "pres_", PETSC_DEFAULT, &fe[1]);CHKERRQ(ierr);
  ierr = PetscFECopyQuadrature(fe[0], fe[1]);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject) fe[1], "pressure");CHKERRQ(ierr);
  /* Set discretization and boundary conditions for each mesh */
  ierr = DMSetField(dm, 0, NULL, (PetscObject) fe[0]);CHKERRQ(ierr);
  ierr = DMSetField(dm, 1, NULL, (PetscObject) fe[1]);CHKERRQ(ierr);
  ierr = DMCreateDS(dm);CHKERRQ(ierr);
  ierr = SetupProblem(dm, ctx);CHKERRQ(ierr);
  while (cdm) {
    PetscObject  pressure;
    MatNullSpace nsp;

    ierr = DMGetField(cdm, 1, NULL, &pressure);CHKERRQ(ierr);
    ierr = MatNullSpaceCreate(PetscObjectComm(pressure), PETSC_TRUE, 0, NULL, &nsp);CHKERRQ(ierr);
    ierr = PetscObjectCompose(pressure, "nullspace", (PetscObject) nsp);CHKERRQ(ierr);
    ierr = MatNullSpaceDestroy(&nsp);CHKERRQ(ierr);

    ierr = DMCopyDisc(dm, cdm);CHKERRQ(ierr);
    ierr = DMGetCoarseDM(cdm, &cdm);CHKERRQ(ierr);
  }
  ierr = PetscFEDestroy(&fe[0]);CHKERRQ(ierr);
  ierr = PetscFEDestroy(&fe[1]);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode MonitorError(TS ts, PetscInt step, PetscReal crtime, Vec u, void *ctx)
{
  PetscSimplePointFunc funcs[2];
  void                *ctxs[2];
  DM                   dm;
  PetscDS              ds;
  PetscReal            ferrors[2];
  PetscErrorCode       ierr;

  PetscFunctionBeginUser;
  ierr = TSGetDM(ts, &dm);CHKERRQ(ierr);
  ierr = DMGetDS(dm, &ds);CHKERRQ(ierr);
  ierr = PetscDSGetExactSolution(ds, 0, &funcs[0], &ctxs[0]);CHKERRQ(ierr);
  ierr = PetscDSGetExactSolution(ds, 1, &funcs[1], &ctxs[1]);CHKERRQ(ierr);
  ierr = DMComputeL2FieldDiff(dm, crtime, funcs, ctxs, u, ferrors);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD, "Timestep: %04d time = %-8.4g \t L_2 Error: [%2.3g, %2.3g]\n", (int) step, (double) crtime, (double) ferrors[0], (double) ferrors[1]);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

int main(int argc, char **argv)
{
  AppCtx         ctx;
  DM             dm;
  TS             ts;
  Vec            u, r;
  PetscErrorCode ierr;

  ierr = PetscInitialize(&argc, &argv, NULL, help);if (ierr) return ierr;
  ierr = ProcessOptions(PETSC_COMM_WORLD, &ctx);CHKERRQ(ierr);
  ierr = CreateMesh(PETSC_COMM_WORLD, &dm, &ctx);CHKERRQ(ierr);
  ierr = DMSetApplicationContext(dm, &ctx);CHKERRQ(ierr);
  ierr = SetupDiscretization(dm, &ctx);CHKERRQ(ierr);
  ierr = DMPlexCreateClosureIndex(dm, NULL);CHKERRQ(ierr);

  ierr = DMCreateGlobalVector(dm, &u);CHKERRQ(ierr);
  ierr = VecDuplicate(u, &r);CHKERRQ(ierr);

  ierr = TSCreate(PETSC_COMM_WORLD, &ts);CHKERRQ(ierr);
  ierr = TSMonitorSet(ts, MonitorError, &ctx, NULL);CHKERRQ(ierr);
  ierr = TSSetDM(ts, dm);CHKERRQ(ierr);
  ierr = DMTSSetBoundaryLocal(dm, DMPlexTSComputeBoundary, &ctx);CHKERRQ(ierr);
  ierr = DMTSSetIFunctionLocal(dm, DMPlexTSComputeIFunctionFEM, &ctx);CHKERRQ(ierr);
  ierr = DMTSSetIJacobianLocal(dm, DMPlexTSComputeIJacobianFEM, &ctx);CHKERRQ(ierr);
  ierr = TSSetExactFinalTime(ts, TS_EXACTFINALTIME_STEPOVER);CHKERRQ(ierr);
  ierr = TSSetFromOptions(ts);CHKERRQ(ierr);
  ierr = DMTSCheckFromOptions(ts, u);CHKERRQ(ierr);

  {
    PetscSimplePointFunc funcs[2];
    void                *ctxs[2];
    PetscDS              ds;

    ierr = DMGetDS(dm, &ds);CHKERRQ(ierr);
    ierr = PetscDSGetExactSolution(ds, 0, &funcs[0], &ctxs[0]);CHKERRQ(ierr);
    ierr = PetscDSGetExactSolution(ds, 1, &funcs[1], &ctxs[1]);CHKERRQ(ierr);
    ierr = DMProjectFunction(dm, 0.0, funcs, ctxs, INSERT_ALL_VALUES, u);CHKERRQ(ierr);
  }
  ierr = TSSolve(ts, u);CHKERRQ(ierr);
  ierr = VecViewFromOptions(u, NULL, "-sol_vec_view");CHKERRQ(ierr);

  ierr = VecDestroy(&u);CHKERRQ(ierr);
  ierr = VecDestroy(&r);CHKERRQ(ierr);
  ierr = TSDestroy(&ts);CHKERRQ(ierr);
  ierr = DMDestroy(&dm);CHKERRQ(ierr);
  ierr = PetscFinalize();
  return ierr;
}

/*TEST

  # Full solves
  test:
    suffix: 2d_p2p1_r1
    requires: !single triangle
    filter: sed -e "s~ATOL~RTOL~g" -e "s~ABS~RELATIVE~g"
    args: -dm_refine 1 -vel_petscspace_degree 2 -pres_petscspace_degree 1 \
          -ts_type beuler -ts_max_steps 10 -ts_dt 0.1 -ts_monitor -dmts_check \
          -snes_monitor_short -snes_converged_reason \
          -ksp_monitor_short -ksp_converged_reason \
          -pc_type fieldsplit -pc_fieldsplit_type schur -pc_fieldsplit_schur_fact_type full \
            -fieldsplit_velocity_pc_type lu \
            -fieldsplit_pressure_ksp_rtol 1.0e-10 -fieldsplit_pressure_pc_type jacobi

  test:
    suffix: 2d_q2q1_r1
    requires: !single
    filter: sed -e "s~ATOL~RTOL~g" -e "s~ABS~RELATIVE~g" -e "s~ 0\]~ 0.0\]~g"
    args: -dm_plex_simplex 0 -dm_refine 1 -vel_petscspace_degree 2 -pres_petscspace_degree 1 \
          -ts_type beuler -ts_max_steps 10 -ts_dt 0.1 -ts_monitor -dmts_check \
          -snes_monitor_short -snes_converged_reason \
          -ksp_monitor_short -ksp_converged_reason \
          -pc_type fieldsplit -pc_fieldsplit_type schur -pc_fieldsplit_schur_fact_type full \
            -fieldsplit_velocity_pc_type lu \
            -fieldsplit_pressure_ksp_rtol 1.0e-10 -fieldsplit_pressure_pc_type jacobi

TEST*/